When health experts gathered in Boston in February for a medical conference hosted by the biotechnology multinational Biogen, they had no idea that kind of history they were going to make.
But according to a new study, the conference helped spread the coronavirus across the country to ultimately infect more than 300,000 people. That comes to about 2 percent of the more than 16 million U.S. cases reported so far by the Johns Hopkins Coronavirus Resource Center.
News that the conference spread the virus was not new. Initially, contact tracing showed about 100 cases were linked to the event, according to CBS. But that was just the tip of the iceberg, researchers found.
A report published in the journal Science that that as of Nov. 1, somewhere between 261,000 and 439,000 cases were linked to the event, with the researchers giving the most likely number of infections as 333,000.
The study came to its conclusions by tracking the genetic code of the virus, according to its lead author.
“It’s as if some viruses have polka dots and others don’t, and we follow those polka-dot viruses across time and space,” Jacob Lemieux, an infectious diseases staff physician at Massachusetts General Hospital, told CBS.
In the Boston region alone, the study estimated that 51,000 cases were linked to the conference. However, the strain of COVID-19 linked to the conference was soon seen elsewhere in the country and abroad, according to CBS.
“That genetic marker started appearing in other states in early March, being especially prevalent in places where conference attendees returned home. Those include Florida, where 29% of the conference-linked cases ended up. was well as Indiana and North Carolina. The strain of virus was also found as far away as Australia and Slovakia,” CBS reported.
Florida ended up with 29 percent of the cases linked to the conference. Cases linked to the conference were also recorded in Australia and Slovakia.
“It’s surprising to the public to realize that a single event can cause so many downstream infections,” Lemieux told CBS.
“These events have been going on since day one — the Wuhan seafood market, ski resorts in Europe, cruise ships, Mardi Gras, a wedding in Maine, the Sturgis motorcycle rally” in South Dakota, he said.
The study noted that not all serious events spread the virus. For example, the study said an outbreak of the virus that killed 24 at a skilled nursing facility was confined to the facility and never spread outside of it.
So what made the conference such a super-spreader event?
Attendees “tended to be younger, healthier, and were traveling more, and we found that they went to a lot of different places,” Lemieux told CBS.
“We don’t think these strains had a propensity to spread more than any other,” Lemieux said, turning to the technical name for COVID-19. “We suspect that these types of events have been happening over and over again, and are major contributors to the propagation and spread of SARS-cov2 throughout the world.”
The report said that it highlighted “the close relationships between seemingly disconnected groups and populations: viruses from international business travel seeded major outbreaks among individuals experiencing homelessness, spread throughout the Boston area including to other higher risk communities, and were exported to other domestic and international sites.”
“It also illustrates the role of chance in the trajectory of an epidemic: a single introduction had an outsize effect on subsequent transmission because it was amplified by superspreading in a highly mobile population very early in the outbreak, before many public health precautions were put in place, and when its effects would be further amplified by exponential growth and subsequent superspreading events (e.g., among the homeless),” the study stated.
The study noted that as society seeks to battle the virus, understanding how it spreads will be important even as a vaccine has emerged to fight off its impacts.
“While superspreading events among medically vulnerable populations, such as nursing home residents, have a larger immediate impact on mortality, our findings raise the possibility that — paradoxically — the implications may be greater, when measured as a cost to society, for superspreading events that involve younger, healthier and more mobile populations because of the increased risk of subsequent transmission,” it stated.
“With the possibility of vaccines that protect against disease but not infection, this consideration may be increasingly important. In summary, this study provides clear evidence that superspreading events may profoundly alter the course of an epidemic and implies that prevention, detection, and mitigation of such events should be a priority for public health efforts,” the study said.
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